Manufacture of ferrous articles



Patented Sept. 20, 1932 umran STATES ear oFFie MANUFACTURE OF FERRO'US ARTICLES No Drawing.

Heretofore in the commercial manufacture of substantially all merchantable ferrous articles, it has been'necessaryin the course of extracting the iron from the ore and convert- 5 ing it into the desired article to reduce the iron at least once to aliquid state. Thus in the case of cast iron articles the iron is liquefied in the blast-furnace from which it is either cast directly into the desired shape or cast into pigs which are again remelted and cast thereinto, while in the case of steel articles liquefaction of the iron takes place both in the blast-furnace and again during the conversion of the metal into steel prepara- 'tory to its subsequent reduction to the desired shape by any of the various methods usually employed therefor.

lfhe present invention contemplates the direct production of merchantable ferrous articles without preceding liquefaction of the metal, which articles may then be utilized without further treatment or may be forged or otherwise treated or machined either with a view to improving the quality of the metal or reducing the articles to a very definite predetermined size and shape or both. Our invention therefore is of material advantage in that deleterious eifects if, any, upon the character and quality of the metal resulting from the liquefaction thereof are avoided while because of the factthat the articles can be produced in approximately the desired finished sizes and shapes and in the case of I hollow-cylindrical articles of substantially perfect concentricity, the subsequent finishing operations, if any, such as forging, machin ng or the like can be performed more readily, more cheaply, and frequently more accurately, with consequent reduction in manufacturing expense, than is possible in the case of similar articles produced by the methods heretofore commercially employed.

By the foregoing reference to possible deleterious efiects resulting from liquefaction of the metal, we do not desire or intend to definitely aver that such efiects do'occur although it is claimed by some metallurgists that such is in fact the case and certaintests would seem to support this view. Therefore if it be a fact that liquefaction of the metal application filed February 9, 1928. Serial No. 338,882.

is injurious, the disadvantages arising therefrom, whatever they may be, are entirely avoided by our invention while, on the other hand, if liquefaction is not actually injurious, other advantages and benefits resulting 155 from our invention and which may be generally characterized as material economy and enhanced efiiciency in the manufacture of various ferrous articles are in no way afl'ected or diminished.

It has long been known 'that substantially pure iron may be produced by heating iron ores or oxides of iron in suitable reducing atmospheres or in contact with reducing materials either solid, gaseous or liquid, by keep- 5%? ing the reducing temperature below the fusion temperature of the materials involved including that of the non-metallic gangue; from the resultant mass the metallic, substantially chemically pure iron, can be separated magnetically in the form of relatively finely divided particles, and is usually known as sponge iron which term we will, for con venience employ herein.

Owing to its finely divided state and relatively large surfaces, this sponge iron is readily oxidized on heating but can be molded cold into almost any desired shape by the application of heavy pressure. The molded articles, so produced, however, are relatively w porous, lack cohesion and strength and are readily oxidized by a moist atmosphere and in this weak and unstable condition are not susceptible of much practical use. It has, however, been found that when such articles are 95 heated to their thermal-critical range or very slightly above it, the iron undergoes certain very definite changes so that upon cooling the individual iron particles in the mass coalesce and render the entire mass more dense than before it was heated, a resultant shrinkage in size or dimensions also taking place presumably because of the more intimate association with the particles in the mass. There may thus be produced an iron mass of predeter- 95 mined form ordinarily having a density intermediate the densities of wrought iron and of steel and which is susceptible of subsequent treatment such as forging and machining or either to produce a finished commercially merchantable article such, for example, as a pipe, projectile or the like.

Moreover before-molding the sponge iron to the desired shape, a predetermined quantity 5 of carbon in pulverized or other suitable form may be mixed therewith, graphite or charcoal being forms of carbon suitable for this purpose, and the mixture of sponge iron and carbon then molded and heated to its thermal-critical range or slightly above as heretofore described and, if necessary, held at that heat until all of the carbon has been absorbed by the iron, thus converting it into steel. Thereafter, following the cooling of the heated mass, substantially the same results as to coalescence and shrinkage are exhibited as in the case of the pure iron so that in this manner a steel article having a predetermined carbon content may be produced without preceding liquefaction of the metal.

In the performance of our invention, therefore, we form sponge iron, or a mixture of sponge iron and carbon, to a predetermined desired shape by exerting heavy pressure on the material while cold and in a suitable mold, the shape of the article so produced approximating that of the desired finished article, for example, a projectile, and then raise the article so molded to its thermaL criticalrange, or slightly above,and allow it to cool so as to coalesce the particles and increase its homogeneity and resistance to oxidation as above described. However, to compensate for the shrinkage of the molded article as it cools, it is of course requisite that it be initially molded to a correspondingly greater size so that the reduction in its various dimensions which takes place as it shrinks shall ultimately bring it to the desired size which may be that in which the article is to be used commercially without further treatment, or if it is to be subjected to further treatment, a size to permit the same, that is,

for example,to permit-a still further reduction in size through a forging operation or the like with resultant additional consolidation of the metal or the removal of a certain amount of the metal by machining or the like to reduce the article to Very definite dimensions or improve its finish. As the said shrinkage is relatively considerable with corresponding reduction in dimensions of the article, it is ordinarily necessary to initially mold the article considerably larger than the size it is desired it shall be after it has been heated and cooled, for example, from 10% to 15% larger, but of course the exact allowance to be made for shrinkage will necessarily vary in different cases in accordance, among other things, with the character of the article, the

pressure employed in molding the same, the

character of the material being molded and other factors which will vary somewhat under different operating conditions.

It is thus apparent that in accordance with tively low cost and of such character that the said further treatment is facilitated and rendered more easy of accomplishment than with the blanks intended for similar treatment heretofore produced by ordinary methods.

Particularly is our invention thus of advantage in the production of hollow cylindrical blanks ultimately intended for conversion into pipes, projectiles and the like for we are able to produce such blanks of substantially perfect concentricity with consequent furtherance and reduction in cost of the subsequent operations to which the blanks are subjected in producing the finished article' Thus, for example, it has heretofore been practically impossible to produce projectile blanks of substantially perfect concentricity when the blank is formed by piercing a solid billet in the customary way with the result that in the subsequent machining operations more metal has to be removed from one side of the blank than from the other which renders the said subsequent operations more diflicult and enhances their cost. By means of our invention, however, we are able to produce a hollow blank intended for similar purposes which is substantially concentric and so close to finished size that it may be brought thereto by merely removing a very small amount of metal substantially equally from all points on its surfaces.

It will therefore be apparent that our inof many articles, and particularly to the production of hollow blanks, in a more economical, accurate and rapid manner than has heretofore been possible by the methods commonly utilized, in consequence of which the subsequent operations incident to the completion or finishing of the article are facilitated and the cost of the finished article materially reduced.

Having thus described our invention, we claim and desire to protect by Letters Patent of the United States:

1. In the manufacture of a ferrous article of commerce, the steps of cold molding sponge iron by means of pressure to a form approximating that ofthe ultimately desired article but of dimensions greater in all directions than said article, and then heating the molded article to its thermal-critical range and allowing it to cool to thereby reduce it to the size ultimately desired.-

2. In the manufacture-of a ferrous article of commerce, the steps of cold molding a mixture of sponge iron and carbon by application of pressure to a form substantiall corresponding to that of the desired artic e but of greater size, heating the molded article to its thermal-critical range, allowin the article to cool, and then subjecting t 0 article to a finishing operation. a

3. In the manufacture of a hollow ferrous article of commerce, the steps of cold molding sponge iron by application of pressure to form a hollow blank of sufliciently great dimensions in all directions to effect a redetermined compensation for shrinkage s15) allowing it to cool to eifect consolidation and coalescence of its constituent particles.

4. In the manufacture of a hollow ferrous article of commerce, the steps of cold molding sponge iron by application of pressure to form a hollow blank approximately the shape of the ultimately desired article and of sufficiently greater dimensions in all directions than said article to compensate for shrinkage after heating, and then heating the blank and allowing it to cool to effect consolidation and coalescence of its constituent particles and a. reduction in its dimensions approximately the amount so allowed for shrinkage.

In witness whereof, we have hereunto set our hands this 6th day of February, 1929.

GUSTAV A. REINHARDT, RICHARD H. EURICH.

sequent to heating, and then heating the blank'and 

